For those new to Raku, it is a Japanese quickfire technique developed in the 16th century originally centered around the Japanese tea ceremony. In the 1960′s a ceramic artist by the name of Paul Soldner brought this technique back to the US and tweaked it a bit, adding a post reduction technique at the end of the firing. In Western ceramics this technique has become quite common, but the original Raku is still practiced today in Japan by the same family line of ceramic artists who originated the technique.

The Raku firing we did this weekend was in the Soldner tradition of American Raku. Pieces were heated in a small kiln designed to heat up quickly utilizing propane as the fuel. The burner we used was a simple weed torch found at Home Depot for about $40. The kiln’s frame was a new design of mine that I was trying out; the square chamber allows for even heat distribution and the sliding top allows for easy access to the ware when lifted. The white material is a refractory fiber called Kaolwool, a 2 inch layer of this lined the kiln walls and acted as insulation. The pieces are then heated to temperature. The temperature for Raku varies depending on the glazes being used. A keen eye can spot when the glazes have melted though and it is time to pull them from the kiln.  Once removed from the kiln the pieces are placed into a combustion chamber, in this case a metal garbage can with a lid. Inside the garbage can we placed torn up newspaper as our combustion source. Any burnable material will work. The pieces are then placed in the combustibles and allowed to burn for a few seconds. The lid is then placed on the can which puts the chamber into a reduction, essentially burning out all the oxygen inside the chamber. For high copper and oxide glazes I like to “burp” the chamber by opening up the lid and allowing the chamber to re-oxidize briefly. This helps some of the colors develop more during the post firing.

A few pictures from the events with a short video of what half the firing is all about.

IMG_1948 <—— Click here for video

I used tables that I already had to pour the concrete onto. This saved a lot of money on extra materials to construct the table base. The only addition I made to the tables was to support the legs with 2×4′s to strengthen the table. For a 6-foot table I was adding about 250lbs of concrete, so it’s important to brace those legs! In the pictures below I show step-by-step how the shorter 5-foot table was made using half concrete/half plaster. We use this as our main wedging table because it gives a nice option between the two materials.

I built the frame to pour into from 1×4′s. This creates the basin to pour the concrete or plaster in. I put a separator down the center to create two basins, one for plaster and one for concrete. For this table I left the perimeter boards attached so the excess length will be cut off later. The concrete was poured to a thickness of 2″. This is plenty thick for a tabletop and not too thin that it will easily crack.

Screw in a wire mesh to the floor of your mold form. This adds extra strength to your table and prevents cracking. Be sure the mesh is fastened below the top level line of the form, but allow space for the concrete to get underneath the mesh. Ideally you want the mesh to be suspended inside the concrete form, not sitting below it.

Pour the concrete. I mixed mine up in a 5 gallon bucket. This section of table is about 1 1/3 bag of concrete. The first 1/3 of  the bag I mixed up relatively dry. Once poured in, I adjusted the wire mesh to make sure it was suspended a little above the first layer of mix. Run a 2×4 across the top to check and make sure the wire mesh isn’t sticking up past the mold. Nothing is worse than pouring the concrete and finding out later that there’s a piece of wire sticking out. The next bag was mixed a little wetter, but still stiff; too liquid of  a mix will result in a weaker table and a less smooth surface. Troll over smooth and let it begin to set up. While you’re waiting, mix up your plaster for the second half of the table.

With the plaster poured it’s now a waiting game. To get a nice smooth finish on your concrete you need to wait until just the right time before you troll it over with a flat blade. As the concrete is setting up run over it with a float to make sure you settle out the larger stones in the concrete, this will help for the final smoothing. Once it’s set up to the point where it is stiff yet still a little malleable. (I poke it with my finger, if it goes in wait a bit longer, if it leaves a finger print you’re good to go, if it leaves no mark, it’s too late). When you get to the right consistency run your blade troll over it, smoothing it out. If it’s at the right maturity you’ll get a super smooth almost glossy (from the moisture) finish. This is what you’re looking for. Once smoothed over let it set another hour or so.

Your next challenge is to keep the concrete (and plaster) wet for as long as you can. Sponging water over it every 20 minutes or so. The longer you can keep it wet, the stronger and more durable of a table you’ll have. Even a few days after you pour it you’re going to want to keep it saturated. Putting a plastic sheet to cover it over night will help.

  Above is a picture of two other tables I poured that were solid concrete. They are 6ft by 30in. The concrete is about 2in thick. These took 3 1/2 bags of 80lb concrete each. The concrete I used was a “quickcrete crack resistant mix.” It was a little bit pricier ($5 per 80lb bag) but well worth the few extra bucks. The crack resistant concrete has small microfibers that help hold the concrete together, a lot like putting fiberglass fibers in your clay. Actually it’s the exact same thing. The plaster I used was “Casting Plaster #1,” you could use Pottery Plaster #1 but the Casting Plaster is a much tougher plaster and won’t chip or scratch as easily.

All in all, I built the 3 tables for under $100 (not including the original price of the table bases), and we now have much better and safer work surfaces for the studio.

A few things to think about:

- This is a ceramic studio, there’s clay and dust everywhere. Artists are urged to cover paintings or drawings in a sealer so they can be wiped down or have their work protected by glass or some other means.

- Penguin Foot Pottery will take 10% of all sales so price your work accordingly.

The first and most obvious step – start with a lot of clay. You can’t make large vessels without large quantities of your material. Keep in mind that you will lose a bit of clay during the process, even more if this is your first time going big.

The larger and taller your piece is, the thicker the walls need to be. A 2 foot tall pot may need walls that are over a half inch thick (depending on the clay body) to support its own weight. In the picture above I have 25 lbs of clay on the wheel.

No, I did not wedge one 25 lb mass of clay. Instead I wedged up two 12-and-a-half pound balls and put them on the wheel one on top of the other. I then patted them together while slowly spinning the wheel. As you pat the clay down try to pat it as centered as possible, this will make centering the clay significantly easier. When centering these amounts of clay, it’s important to put your whole body weight into it, sometimes standing up and leaning into it will help. All the same principals of centering still apply: make sure you are compressing the clay at the proper angle from the side and compacting the clay downwards from the top. Because the mound is so much larger, you may have to move your hand up and down or use two hands on the side to get enough of a push.

Pulling the clay has, again, all the same principles. Compress the clay at 5 o’clock and slowly pull up. This of course is much easier said than done. Make sure your body is braced and your arms tucked in tight. For the first few pulls, when I’m moving the most amount of clay, I like to use one of those large yellow clean up sponges as my outside hand. I make a fist with the sponge covering my knuckles and then push that against the outside. This gives a much sturdier compression against the clay and the sponge allows for a smooth transition. Don’t try to pull it all up at once! Think of your first pull as a centering pull. Move the clay up a little but mostly move the clay into a good position for your next pull. Keep your base thick, the base of your pot is what’s holding all the clay up, if this thins out too quickly you’ll get torquing or it will flop in on itself.

In the picture above you’ll see a fan blowing on the piece while I’m working on it. This is key. A torch is also a helpful tool for making larger pieces. Because so much of your hands is touching the surface of the clay, you’ll need to be using a significant amount of water. When the walls of your piece get over saturated it will start to slump back into itself. After a pull or two use your metal rib to scrape the slip off the surface, then let the piece spin in front of the fan for 10 minutes or so. This allows the piece to dry out a bit between pulls and allow you to have thinner walls without it slumping in.

Shaping large forms can be tricky. Sometimes different tools are needed to get a desired shape. Many potters make their own tools as they progress in their work. Before you begin to shape your piece let it spin in front of the fan for 20-40 min. Allow it to dry out some and stiffen up, this will keep your form’s shape much tighter and allow you to stretch the clay further. Keep in mind that when you open up a form into a more bulbous shape, you’re going to lose some height, several inches in fact, depending on how wide it is. When stretching the clay outwards be sure to come back on the outside and compress the clay with a metal rib. This will keep your form nice and tight. While shaping the piece keep the base nice and thick, this will help keep your form balanced while you push and stretch the clay. The base can always be trimmed off with a fettering knife, this is one of the last steps before you allow the piece to begin to dry.

Finish off your work and cut away any excess clay at the base. This could be done when it’s leather hard – utilizing trimming tools. To allow the piece to dry to that state more evenly, it is important to trim away as much as you can. Wrapping the rim in plastic is another alternative.

Now take your big piece home, show it off to everyone you know, and bask in the Texas-sized praise.

For more throwing large action, check out this tutorial video “How to Throw Large Forms on the Wheel.”

For all the vintage revivalists out there I humbly submit my apologies for this vinyl blasphemy ahead of time.

A “bat” is a tool potters use to place on the wheel head while they work on their piece. The bat is then lifted off without a need to warp or stretch your creation; particularly useful when creating plates or platters that are difficult to slide off the wheel. Bats are made from many different materials: masonite, plastic, plaster, wood and just about anything else that a potter can cut round and drill holes into.

When I heard that someone was using LP’s I had to investigate further, so I went to my local record store. I found myself at Logan Hardware, which if you are ever in Chicago and have a love for records and vintage arcade games, this is your heaven. Not only do they have an awesome selection of LP’s, they also have an arcade museum in the back with all the vintage games set to free play – AMAZING! As most records stores do, they had a 25 cent box of old records that were most likely damaged or discarded (this box was nearly all Disco music, hence the name Disco Bats). I grabbed myself a few and was on my way, after a few rounds of Teenage Mutant Ninja Turtles and Doctor Who pinball of course.

Back at the studio I used silicone to adhere two or three records together to stiffen them up and get a good thickness so the bat pins weren’t sticking out. After a bit of drying I measured out the hole distance, drilled and bam – I had myself a 75 cent bat. Now considering that your average plastic bat will run you around $10-$12, I am quite satisfied. The icing on the cake for me was that if I took my sharpened needle tool and got the wheel going at just the right speed, you could just start to make out those old funky tunes.

How To Throw a Plate:

Throwing a Square Cup:

Before I start any large form I will usually throw one or two smaller forms to warm myself up. While throwing the smaller ones keep a close eye on your mechanics. Focus on where you’re putting pressure on the clay as you center the piece and what angles you are pushing at the clay to open and pull. Sometimes when we throw smaller forms with less clay we become careless and our throwing mechanics can get sloppy because we have the strength in our hands to overcome it. With the larger amounts of clay (over 12lbs) proper angles and mechanics become exceedingly important.

Something to think about when you are throwing large amounts of clay: brace yourself! The clay is going to want to push you around, if your body isn’t properly braced you may find yourself at the mercy of the clay. Don’t try to pull all the clay up at once. With less clay sometimes it’s easy to get your height in just two pulls, you’re not going to do this with a lot of clay; nor should you. Keep the base thick – you’re better off trimming later than reaching 16 plus inches and having your piece collapse from underneath. It’s important to remember that as your clay gets taller it needs to be thicker in order to support its own weight.

Throwing Large Forms:

Double-Walled Vessel on the Wheel:

Throwing a Bottle Neck form: